Method and apparatus for collecting soil gas samples



' INVENTOR Josephfla/dmh C/aPk AKWW ' ATTORNEY J. B. CLARK Dec. 27,1938.

METHOD AND APPARATUS FOR COLLEKJ'IINC: SOIL GA$ SAMPLES Filed Oct. 13,1937 Patented Dec. '27, 1938 PATENT OFFICE METHOD AND APPARATUS FORCOLLECT- ING SOIL GAS SAMPLES Joseph Baldwin Clark,

Tulsa, Okla., assignor to Stanolind Oil and Gas Company, Tulsa, Okla, acorporation of Delaware Application October 13, 1937, Serial No. 168,781

9 Claims.

This invention relates to geophysical prospecting and particularly toanimproved method and apparatus for conductingvthe same by removingsamples of soil gas from beneath the earth's surface and quantitativelyanalyzing the same for the presence of hydrocarbon.

It has been found that minute traces of hydrocarbons present in soilgases are an index of the presence of coal, oil or gas at greaterdepths.

In collecting soil gases for analysis it must be assured that resultscan be duplicated and that all conditions are reproducible since asurvey depends on relative results at a large number of points.

One of the chief difliculties encountered in practicing heretofore knownmethods with available apparatus has been the contamination of the gassample by surrounding gases which gain access thereto. Thiscontamination may be in the form of air which has the effect of reducingthe concentration of hydrocarbons to a non-reproducible degree or it maybe in the form of stray hydrocarbon vapors, as for example, gasolinevapors which are always present in thickly populated areas. v

It is an object of this invention to provide'a method and apparatus forremoving samples of gas from below the earth's surface, particularly atrelatively small depths, wherein the sample of gas is maintained freefrom contamination by surface or other foreign gases, and in which thesample is truly representative of the gas at and below the point fromwhich it is-removed.

The above and other objects, advantages and uses of my invention willbecome more apparent from a reading of the following specification andclaims taken in connection with the appended drawing which forms'a partof this specification,

and wherein:

Figure 1 is a diagrammatic elevation partially in cross-section showingthe relative positions of the parts of my improved apparatus at an earlystage of its installation;

Figure 2 is a diagrammatic elevation partially in cross-section showingthe relative positions of the parts of my improved apparatus at asubsequent stage of its installation; and

Figure 3 is a diagrammatic elevation partially in cross-section showinga complete assembly of my improved apparatus and the disposition ofparts following the final stage of its installation.

In accordance with my invention, I have provided an improved arrangementof apparatus and method of installing the same, by means of which a truesample of gas is obtained uncontaminated by surface gases such as otherhydro- .carbons or air.

An outer tubular sleeve III of a length slightly greater than the depthfrom the surface of the earth to the point at which a sample is to beremoved receives telescopically an inner tube H, the outside of which issealed relative to the inside of the tubular sleeve by means of apacking seal l2.

Inner tube H has a very narrow bore, preferably approaching capillarydimensions, so that it will hold as little of the sample as possible.

The lower end of inner tube H has attached thereto, as by a threadedconnection, spear head l3, having a point It and an enlarged headportion IS.. The outer diameter of the enlarged head portion l5corresponds to the outer diameter of the tubular sleeve in and includesa shoulder l6 against which the lower end I! of the tubular sleeve inrests in the telescoped position of the parts. While I have shown spearhead I3 threaded on the lower end of inner tube H, and. prefer this formsince it is easier and cheaper to manufacture and facilitates cleaning,I also contemplate as coming within the scope of my invention anarrangement wherein head I3 is integral with inner tube II. In this casethe upper enlarged head 36 of inner tube ll must necessarily be threadedonto tube li rather than an integral part of it as shown in the drawing.

Inner tube H is provided with ports l8 formed by a lateral passagetherethrough in communication with the inner periphery l9 thereof.Formed in the outer periphery of inner tube II are gascollecting grooves20 parallel with the axis of the tube and in communication at theirlower ends with ports I8. A wick 2| is received within the lower end oftubular member Ii for the purpose of keeping foreign material out of theinner bore l9. 'It will thus appear that with tubular sleeve l0 andinner tube I i in telescoped position, ports l8 are covered by the lowerend of the tubular sleeve Ill and that by relative movement betweenthese two members ports it are uncovered.

As a particular arrangement of means for effecting the lowering into theground of tubular sleeve l0 together with inner tube Ii while intelescoped relation to each other, I provide large cap 22 (Figure l)which fits over the upper end of. inner tube II and engages the upperend of outer tubular sleeve ID. The assembly is then driven down as bymeans of a hammering operation. When the telescoped assembly has beenlowered to the desired depth large cap 22 is replaced by small cap 23(Figure 2) fitting over the upper end of inner tube I I out ofengagement with-the outer tubular sleeve l0 and the hammering operatlonis continued to eflect the further lowering of the inner tube H relativeto the outer tubular sleeve l0, thereby uncovering gas entry ports l8.

Referring particularly to Figure 3 it will be seen that by furtherlowering inner tube ll relative to tubular sleeve III, the large portion15 of ,spear head 13 produces an annular space about the lower portionof the inner tube l'l between the lower end I! of the outer tubularsleeve l0 and the shoulder l6 of the spear head l3. As a furtherassurance that the gas will have ample space in which to collect,vertical grooves 20, above referred to, are provided in the side wallsof inner tube II in communication with ports I8.

Arranged for attachment to the upper end of the inner tube II is asample receiver 24 connected thereto through conduit 25 and valve 25.Conduit 25 terminates in nipple 21 which extends within sample receiver24 adjacent to but short of the top thereof. Filler conduit 28containing valve 29 provides means for filling sample receiver 24 withwater or other suitable liquid as will appear. Gauge glass 30 orequivalent means is provided for determining the level of the liquidwithin the sample receiver 24. This sample receiver is connected throughconduit 3| and valve 32 with trap 33. An extension nipple 34 passes downwithin trap 33 to a point adjacent to but short of the bottom thereof.An efllux tube 35 having a pivotal connection with trap 33 is providedto control the flow of liquid from sample receiver 24.

As a means for additionally sealing the entry ports l8 of inner tube Hfrom surface gases, I employ a sealing mud or gel such as a bentonitemud slurry 31. This sealing material is used about the upper portion ofthe outer periphery of the tubular sleeve l0 and is introduced inaccordance with my novel method as will appear. Other plastic or viscousfluid sealing materials can, of course, be used.

Method of installation and operation A hole is first formed in the earthas indicated in Figure 1. This hole is made sufiiciently large toreceive the outer tubular sleeve Ill and of a depth which is only afraction-preferably from one-fourth to one-half of the depth to thepoint at which a sample is to be removed. This hole is next filled atleast partially with a sealing material such as gel mud, preferably abentonite mud slurry 31. The tubular sleeve I0 and inner tube l l arethen introduced into the hole and lowered while in telescoped relationto a point adjacent that from which the gas sample is to be removed.This lowering is preferably effected by a hammering operation; however,any other means such as pressing can be employed. In effecting thelowering of the members by a hammering operation, the large driving cap22 shown in Figure l is first employed.

When the tubular sleeve [0 and the inner tube II have been lowered inunison to the desired point, the enlarged cap 22 is removed and isreplaced by small driving cap 23 fitting about the head of inner tube 1l. The inner tube H is then driven to an additional depth below the endof the tubular sleeve Ill, thus exposing gas entry ports l8 to the entryof gas therethrough and into the inner bore H of the inner tube l I.

The sample container 24 together with the trap 33 is next attached inplace on the upper end of inner tube H, as indicated (Figure 3). "Nextvalves 23 and 32 are closed and water is introduced into samplecontainer 24 through conduit 28 and valve 29 to fill the containercompletely, following which valve 29 is closed.

-Altematively, the sample container can be fllled by the use of valves26 and 32, before the sample container is attached to inner tube II, andfiller conduit 28 and valve 29 can be omitted.

Valve 32 is then opened and the water in sample receiver 24 is allowedto run out slowly through trap 33 and eillux tube 35, thus creating apartial vacuum within sample receiver 24 and causing the soil gases tobe sucked up through inner bore I9. The rate of flow is controlled bythe position of eillux tube 35 and a standardized rate of flow is usedto insure reproducible conditions. When the soil gas sample has beencollected valves 26 and 32 are closed and sample receiver 24 is removedwith the valves from the top of inner tube H and taken to the laboratoryfor quantitative analysis of the sample contained therein.

While I have described the introduction of the sealing material prior toplacing the tubular sleeve and inner tube in the hole, and prefer thisorder of procedure, it is to be understood that it maybe deviated fromwithout departure from the spirit and teaching of my invention, as forexample, the tubular sleeve and inner tube may be introduced first intothe hole shown in Figure 1 and then the sealing mud added eithe prior tothe beginning of the hammering operation or shortly thereafter.

Although a particular form of spear head is shown, and I prefer thisform as being the more eflicient, I nevertheless contemplate otherequivalent forms such for example as a spear head, the large end I5 ofwhich is slightly larger than the outside diameter of the tubular sleeveI0. Basically the important thingto note is that the relative movementof the inner tube with respect to the tubular sleeve uncovers a. gasentry port and thereby provides a most efficient means of removing a gassample. The relative movement need not be a sliding movement, althoughthis is preferred, but may for instance be a rotational movement touncover the ports.

While I have described my invention in relation to one embodimentthereof, I desire it to be understood that I contemplate all equivalentsand intend to be limited only as indicated by the appended claims whichshould be construed as broadly as the prior art will permit.

I claim:

1. An improved method of installing an elongated apparatus for removinga sample of soil gas from below the earth's surface, said apparatusincluding a hollow gas-collecting member open at or near its lower end;said improved method comprising first forming a hole in the earth ofsufiicient cross-section to receive said elongated apparatus but of adepth which is only a fraction of that to the point at which the sampleof gas is to be taken, at least partially filling said hole with asealing agent, placing Within said hole said elongated apparatus,driving said elongated apparatus to a depth at which a. sample of gas isto be taken, and withdrawing through said hollow gas-collecting member asample of soil gas to be analyzed, said sealing agent serving to preventthe contamination of said soil gas sample with atmospheric air.

2. An improved method of installing apparatus for removing a sample ofsoil gas from below the earths surface, including an outer tubularsleeve,

and an inner tube telescopically received within the tubular sleeve,atleast one opening through the wall or the inner tube communicating withthe bore thereof, this opening being normally covered by the lowerportion of the tubular sleeve when the parts are in telescoped relationbut being uncovered upon relative movement between the sleeve and innertube; said improved method comprising first forming a hole-in the earthof sufildlent cross-section to receive the tubular sleeve but oi! adepth which is only a fraction of that to the point at which the sampleor gas is to be taken, at least partially filling said hole with asealing agent, placing within said hole said tubular sleeve and innertube contained therein in telescoped relation, driving said sleeve andtube while in telescoped relation to a point adjacent which a sample 01'gas is to be taken, driving said inner tube to a still further depththereby exposing said opening therein to the entry of gas, and removinga sample of gas to be analyzed from the upper portion of said innertube.

3. Apparatus for removing a sample of soil gas from beneath the surfaceof the earth comprising a gas-collecting tube adapted to be driven intothe earth, said tube having at least one port for the entrance of soilgases into its interior, means to cover said port while said tube isbeing driven into the earth, means operable from above the surface ofthe earth for uncovering said port,

after said tube has been driven into the earth, means for collecting asample of said soil gas at the top of said tube, and means forpreventing the intrusion of atmospheric air into said tube.

4. Apparatus for removing. a sample of soil gas from beneath the surfaceof the earth comprising, an outer protective member an inner hollowgas-collecting member received within said outer protective member, saidinner hollow gas-collecting member being provided at or near its lowerend with at least one opening through the wall thereof communicatingwith its interior, said opening being covered by said outer protectivemember when said two members are in one relationship to each other, butuncovered by relative movement between said two members, said twomembers being arranged to be lowered together through the earths surfaceto a point adjacent which a sample of gas is to be taken, and means formoving said two members relative to each other to uncover said opening.

5. Apparatus for removing a sample of soil gas from beneath the surfaceof the earth comprising, an outer tubular sleeve, an inner tube receivedwithin said tubular sleeve, said inner tube having its lower end closedand provided with at least one opening through the wall thereofcommunicating with its interior, said opening being covered by saidtubular sleeve when the inner tube and outer tubular sleeve are in onerelationship to each other, but uncovered by relative movement betweensaid sleeve and said inner tube, said sleeve and said tube beingarranged to be lowered through the earths surface to a point adjacentwhich a sample oi. gas is to be taken, and means tor moving said tubularsleeve and said inner tube relative to each other to uncover saidopening.

6. Apparatus according to claim 5 including a gas-tight seal betweensaid tubular sleeve and said innertube located above said opening.

'7. Apparatus for removing a sample of soil gas from beneath the surfaceof the earth comprising, an outer tubular sleeve and an inner tubetelescopically received within said tubular sleeve, said inner tubehaving its lower end closed and provided with at least one openingthrough the wall thereof communicating. with its interior, said openingbeing covered by said tubular sleeve when the inner tube is intelescoped relation with said outer tubular sleeve, but uncovered byrelative movement between said sleeve and said inner tube, said sleeveand said tube being arranged to be lowered through the earth's surfaceto'a point adjacent which a sample of gas is to be taken and said innertube then lowered through said tubular sleeve to a still further depththereby uncovering said opening for the entrance of gas to the interiorof said inner tube to be removed therethrough and analyzed.

8. Apparatus for removing a sample of soil gas from beneath the earthssurface for analysis comprising an outer tubular sleeve, an inner tubetelescopically received within said tubular sleeve, and a spear head,said inner tube being closed at its lower end by said spear head, saidspear head in the telescoped position of said parts presenting ashoulder against which the lower end of said tubular sleeve rests, saidinner tube having at least one opening therein in communication with itsinterior, said opening being covered by said tubular sleeve in thetelescoped position of said parts but uncovered upon relative movementthereof, said tubular sleeve and said inner tube being adapted to belowered to the desired depth in telescoped relation following which saidinner tube is lowered relative to said tubular sleeve to a still furtherdepth, thus defining an annular chamber about said inner tube and thusexposing said opening to the entry of gas into the interior of saidinner tube for removal and analysis.

9. Apparatus for removing a sample of soil gas from beneath the surfaceof the earth comprising, a gas withdrawal tube driven into the earth andopen at or near its bottom, means for sealing said tube against theadmission of surface air, a sample receiving container in communicationwith said tube at a point near the top of said tube, said containerbeing adapted to be filled with liquid, means for draining said liquidto draw a soil gas sample into said container through said tube, meansfor controlling the draining of said liquid from said container, andmeans for sealing and disconnecting said container after a sample hasbeen collected.

JOSEPH BALDWIN CLARK.

